Webster's Revised Unabridged Dictionary · 1913

Trinitarian

Trinitarian , adjective

[Compare French trinitaire. See Trinity.]

Of or pertaining to the Trinity, the doctrine of the Trinity, or believers in that doctrine.

Trinitarian , noun

1.
One who believes in the doctrine of the Trinity.
2.
(Ecclesiastical Hist.) One of a monastic order founded in Rome in 1198 by St. John of Matha, and an old French hermit, Felix of Valois, for the purpose of redeeming Christian captives from the Moslems.